Benefit of two heaters
 

Hi,
I have two 250W heaters in my sump for my 120G.
There are controlled by an aqualogic controller.
My question is is there any real benefit to having two heaters in the sump, apart from warming quicker? Which once you are up to temp is negligible.
I could understand two in a large DT tank, at opposite ends.
Cheers,
Harley

I have 3- 300W heaters in my 150 gal sump/77gal DT.
Redundancy, Redundancy, Redundancy.
Usually I have only ever seen 2 heaters on at a time, but if 1 ever fails, not that big a deal, 2 heaters go - you're in trouble but not dead... yet.
When I get my 210 going, I'll probably get another 3 - 300W heaters and have all 6 in there.

Thanks. I guess if you are ever away for several hours/days, you could get a few degrees temp drop. So, a back up isn't a bad idea there.
But, how many degrees and over what period are we talking before it's a major issue?
If I understand correctly, it's more of a sudden temp jump that's an issue.

I lost $$$$ when I ran 1 heater because it failed. If i would have had 2 (like I do now and will forever) the second would have picked up the slack. I rarely check temps (even though I know I should) so the redundancy is key. Also my tank is in the basement so it dropped rather quickly to a chilly 68f over the weekend.

It would take a while for a tank to cool off enough to cause problems, however for some reason heaters rarely fail in the off position. For this reason two small heaters is better than one large heater, however two large heaters is worse than one large heater. Hopefully that makes sense but ideally if a heater fails in the on position it shouldn't be able to cook the tank. Not so much an issue with external controllers.

BTW I also agree with redundancy like others have talked about but don't forget about control redundancy as well. If you run multiple heaters all large enough to do damage an external controller for temp control would be a wise addition.

I run two heaters my self as well i keep one a couple degrees colder just incase the primary one fails, the tank will only be a couple degrees colder than until the primary one gets replaced,

I think I see what your saying sphelps - basically if you have 2 large and they somehow both fail, then you get a rapid rise. However, I do have the temp controller, so the odds of all 3 devices failing would be more in line with the lottery odds - no?

With two large heaters only one would have to fail on to cook the tank which can happen faster than it cooling off and livestock tends to be sensitive to heat vs cold. Also two heaters means twice the chance of this failure mode. And yes external controller can help prevent it. Usually people set heater temp slightly higher than the external controller temp for added safety.

Yeah, that's why in my mind I prefer several (3-4) smaller heaters. I also have a basement sump that sucks the heat out of my system. If one fails on or off, no big deal. On a 200-300 gallon system, if one or 2 even, get stuck on, definitely needs fixing, but shouldn't cause a catastrophic failure.
But that also means you have to pay attention to your system. You don't want one broken heater to be doing all the heating :) You should know if they're switching on and off.